"Wrack"'s meanings (wreck, destroy, ruin usw.) are close enough to "rack"'s
for the words to be confused. For instance, I'm sure I've seen "wracked with
pain".
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How curious. Can't recall seeing these words in written form in a long time,
though familiar with both ("sea-wrack" etc. in poetry?). My first impulse
would have been "wrack my brain....." but then, until 1975, I consistently
spelled _lizard_ with two z's, a la _blizzard_ (doctoral committee very
kindly pointed out the error, necessitating several annoying corrections).